1. Field of the Invention
The present invention relates to a method for fabricating a semiconductor device by using an etching polymer and, in particular, to an improved method suitable for a process having a small photoresist margin during the trench etching process, by generating a polymer on a surface of a photoresist film pattern used as an etching mask. By generating this polymer on the surface of the photoresist before the trench etching process, and employing the polymer as a protective film for preventing photoresist erosion during the etching process, the present method improves the etching resistance of the photoresist.
2. Description of the Background Art
When a semiconductor device is fabricated using a method having a design rule below 0.10 xcexcm, the increase in trench depth and reduction in design rule require that the thickness of the photoresist mask is reduced in the shallow trench isolation (STI) process. Accordingly, the etching margin for the photoresist mask becomes excessively small in a trench etching process. In some cases, the photoresist film will be eroded during the trench etching process, making it impossible to etch the desired pattern into the semiconductor substrate while maintaining the desired degree of dimensional control.
Accordingly, an object of the present invention is to provide a method for fabricating a semiconductor device by using an etching polymer which can improve the etch selectively or etch ratio with respect to a photoresist, by generating a polymer on the photoresist surface, and employing this polymer as a protective film for preventing photoresist erosion during the trench etch process, particularly for semiconductor devices fabricated using methods with a design rule below 0.10 xcexcm.
In order to achieve the above-described object of the present invention, a method for fabricating a semiconductor device by using an etching polymer, includes the steps of: forming an insulating film having a stacked structure comprising a pad oxide film and a hard mask layer on a semiconductor substrate; forming a photoresist film pattern that exposes a device isolation region on the insulating film; etching the insulating film using the photoresist film pattern as an etching mask to expose the semiconductor substrate; forming a polymer layer on the surfaces of the photoresist film pattern and the insulating film pattern; form a trench for device isolation, by etching the exposed semiconductor substrate using the polymer layer as an etching mask; and forming a device isolation film in the trench.